Between 1979 and 1984 11 cases of fulminant hepatitis were seen at the Department of Infectious Diseases in Lund, Sweden. Four cases were associated with hepatitis B virus (HBV) infection. Besides, all 4 patients had serological evidence of delta infection. Two were considered to be simultaneous HBV and delta agent infections, the other 2 were found to be delta superinfections in chronic HBsAg carriers. All 4 patients were intravenous drug addicts. The other 7 cases of fulminant hepatitis had no serological evidence of neither hepatitis A nor B virus infections and none of them were intravenous drug addicts.